Described below is a device similar to an electrochemical camera for detecting chemical or biochemical substances in liquids, a method for producing the device and the use thereof.
The detection of substances in liquids is gaining more and more in importance both in chemistry and in biochemistry. In this case, use is increasingly being made of electrochemical sensors which, for space reasons, are arranged on a carrier in the form of an array. Possible materials for the carriers are semiconductor materials such as, for example, silicon Si, germanium Ge or gallium arsenide GaAs. When these materials are used, semiconductor technology enables the integration of circuits for signal processing and evaluation of the signals of the electrochemical sensors on the same carrier on which the sensor array is situated.
Since the carrier material Si, Ge or GaAs is expensive and complicated to produce, attempts are made to form structures such as sensors, for example, as small as possible. In this case, care should be taken to ensure reliable functioning. In general, a sensor has finger-shaped interdigital electrodes, having an extremely small structure width in the range of micrometers. Inter alia, gold, platinum, silver-silver chloride or other metals are appropriate as electrode materials. The sensors are arranged regularly on the surface of the carrier, at distances from one another in the range of from a hundred nanometers to several millimeters.
In order to be able to detect chemical or biochemical substances in a liquid electrochemically, the electrodes are coated with molecules which interact with the substances. The interaction is directly or indirectly electrochemically detected. Different sensors are coated with different molecules, such that different chemical or biochemical substances can be detected in the liquid.
The sensors or individual electrodes are often coated by spotting molecules onto the sensors. As the structure size of the sensors and electrodes decreases, however, this becomes more and more complicated. In the case of electrode sizes in the nanometers range, a coating can no longer be effected by spotting. Expensive and complicated methods such as photolithography, for example, are used to apply molecules specifically to the electrodes. A precise alignment of the equipment during coating is necessary and makes the method for producing the sensor arrays susceptible to faults and expensive.